Many thousands of the simple pocket flashlight to which this improvement invention relates have been made and sold. As shown in Stone Pat. No. 3,796,869, the flashlight is designed to be used until the dry cells forming the battery are exhausted and the entire flashlight is then thrown away. As shown in Halliday U.S. Pat. No. 4,032,773, the individual cells may be removed and replaced by fresh cells and continued use of the flashlight.
As exemplified by the simple pocket flashlights described in these two patents, the unit consists of a pair of small dry cells spaced apart and supported by a body of insulating material. The flashlight lamp is permanently connected in series between the positive terminal of the first cell with the negative terminal of the second cell, the negative terminals of both cells being the exposed metal cans of the two cells. The very simple switch consists of a spring wire connected at one end to the positive terminal of the second cell and extending diagonally downwardly toward the metal can negative terminal of the first cell. This structure is covered by a flexible jacket through which the switch wire may be pressed inwardly until the end of the wire remote from its connection with the positive terminal of the second cell makes electrical contact with the negative terminal of the first cell to thereby complete the series lamp circuit. When the pressure is released, the switch wire springs back to its normal position out of contact with the first cell negative terminal whereupon the light is turned off.
It has been observed that in use a significant number of these flashlights exhaust their batteries as a consequence of the unintended lighting and burning of the flashlight due to inadequate spring force to hold the switch wire out of closing contact against even slight pressure that may be exerted while the flashlight is resting in a pocket or otherwise at repose in contact with other objects.
When the cells of the flashlight battery are exhausted due to either the intended or unintended closing of the operating circuit, the batteries must be discarded promptly to avoid damage from the highly corrosive liquid that may escape after a short time from the exhausted cells. The face of exhaustion of the battery is noticeable to the user when the light is intentionally turned on but when the circuit is closed while the flashlight is resting somewhere and the light is not noticed, damage from the corrosive liquid is a real danger.
The object of this invention is to improve the dependability of spring-operating switch by increasing the strain imposed in the switch wire when closing the switch so that a greater force will ensure that contact is broken and the circuit will remain open when the manually applied pressure has been released to turn out the light even in the event of the application of unintended small pressures to the area of the jacket overlying the switch wire. To accomplish this objective, the wire is formed to provide a fulcrum bearing against the surface of the insulator body between the two cells serving to essentially limit the bending of the wire to the portion between the fulcrum and the switching contact remote end of the switch wire. Thus, instead of distributing the bending throughout the length of the wire from the point of attachment to the positive terminal of a cell to the remote end contact, involving a gentle and weak stressing of the wire, the same distance of movement of the contacting end of the switch wire to engagement with the negative terminal of the other cell is limited to the end portion, only, of the wire imposing greater stress and greater loading of spring tension to dependably effect disconnection when light is not desired.